Mingshui Li

Influence of aerodynamic configuration of a streamline box girder on bridge flutter and vortex-induced vibration

Streamline box girders are widely applied in the design and construction of long-span bridges all over the world. In order to study the influence of modifications of aerodynamic configuration and accessory components on flutter and vortex-induced vibration (VIV), more than 60 cases were tested through a 1:50 scale section model. The test results indicates that the aerodynamic configuration and accessory components of streamline box girders can significantly affect the wind-induced vibration of bridge, which is in good agreement with the experience of past researchers. From the tests carried out, it is observed that if the horizontal angle of the inclined web of the streamline box girder is below 16°, the critical flutter wind speed of bridge will increase remarkably, and the VIV will diminish. The test results also show that the 15° inclined web can restrain the formation of vortex near the tail, and consequently improve the performance of aerodynamic stability of long-span bridges. Finally, a new streamline box girder with 15° inclined web was presented and strongly recommended in the aerodynamic configuration design of long-span bridges.

Experimental investigation on the unsteady lift of an airfoil in a sinusoidal streamwise gust

The unsteady lift of a stationary airfoil encountering a sinusoidal streamwise gust is experimentally investigated under attached flow conditions. The airfoil has an NACA 0015 profile with a chord length c = 0.5 m. The Reynolds number of the main flow is in the range of 198 000 ⩽ Re ⩽ 331 000. The reduced frequency of the perturbation ω ranges from 0.047 to 0.392. The results show that the fluctuation in the lift force reduces very much at the high frequency. It can be attributed to a significant reduction in the fluctuating pressure difference over the front half of the airfoil. Thus experimental aerodynamic admittance functions for the unsteady lift are lower than theoretical predictions relating to this case with increasing reduced frequencies, though experimental values are close to theoretical values at low reduced frequencies.

Investigation of Influence Factors on Drag Coefficients for Stay Cables

INVESTIGATION OF INFLUENCE FACTORS ON DRAG COEFFICIENTS FOR STAY CABLES Zhiguo Li , Mingshui Li, Jiadong Zeng Haili Liao 1 Lecturer, School of Civil Engineering, Southwest Jiaotong University,Chengdu,China, lizhiguo@swjtu.cn 2 Professor, School of Civil Engineering, Southwest Jiaotong University,Chengdu,China, lms_rcwe@1 .com PhD Student, School of Civil Engineering, Southwest Jiaotong University,Chengdu,China, zjd_rcwe@163.com Professor, School of Civil Engineering, Southwest Jiaotong University,Chengdu,China, hlliao@swjtu.cn

A Study on Spatial Correlation and Power Spectrum of Natural Wind at Xihoumen Bridge

In design of a long-span bridge, gust response of the bridge is very important and must be taken into account. The long-span structure has low natural frequency, small mass and extremely low inherent damping. The spatial correlation and spectrum of the wind in the low-frequency range affect the gust response However, there are very limited field data about spatial correlation of natural wind and wind spectrum. In the wind-resistance design, the decay factor is set to be 7, which affects the wind-resistance design of a long span bridge. Therefore, natural wind were measured at Xihoumen Bridge and the wind speed spectrum and spatial correlation are calculated. The results show that the spatial correlation of the natural wind is lower than that specified in the wind-resistance design specification of China in the low-frequency ranges. The most appropriate wind spectrum and decay factors fitting to the field measurements are recommended. This means that there is a possibility of being able to modify the design specification of long span bridge concerning gust response. The calculated results provide credible technical guide to construction of Xihoumen Bridge and ensure wind resistance safety.